Apparatus for extruding organic plastic material



June 20, 1950 M. 'MARTIN 2,511,986

APPARATUS FOR DING ANIC PLASTIC MATERIAL Filed April 3o, 1948 2 Sheets-sheet 2 /N l/E/v To $.M. MAR

ATTORNEY Patented June 20, 1950 APPARATUS FOB EXTRUDNG ORGANIC PLASTIC MATERIAL Samuel M. Martin, Baltimore, Md., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application April 30, 1948, Serial No. 24,153

3 Claims.

This invention relates to apparatus for extruding organic, plastic material, and particularly to apparatus for extruding insulating or jacketing material on conductors or other cores.

An object of the invention is to provide new and improved apparatus for eXtruding organic, plastic material.

In utilizing much of the rubber and plastics insulating and jacketing equipment available today, the centering of a conductor with respect to the material extruded therearound sometimes is accomplished by adjusting the components of the extruding head manually at each setup for a given combination of conductor and material. Even when skilled operators are employed, a considerable amount of operating time is lost in making the adjustments necessary to produce commercially acceptable products.

Much of this time may be saved by the use of a so-called self-centering extruding head, which essentially is a head in which the component parts are designed to be assembled in a given position for each setup without any adjustment of the parts. With the use of self-centering heads, the relative positions of the several parts of the head are fixed and the extruding tools are placed in their proper operating position each time the head is assembled. One type of self-centering head is shown in G. L. vCherry et al. Patent 1,862,005, granted June 7, 1932.

The quantity of now of an extrudable material through extruding heads should be balanced, and one of the principal causes of eccentricity in coverings applied to conductors is the presence of unbalanced flow conditions in different portions of the extruding heads. This is especially true when stranded conductors or cabled cores are covered, and the need for balanced iiow conditions is increased when such articles are to be covered with an extruded covering.

In accordance with this invention, a balanced ow of covering materials in Vextruding heads is obtained by spacing the extrusion orifice far enough from the deilector of the core guide that the pressures at all points in the extrusion oriice are equal. As a result, the coverings on covered conductors made with extruding apparatus embodying the invention are substantially concentric with the conductors, whether the conductors are solid or stranded, and the covered conductors meet the standards for commercially acceptable pro ducts.

The invention will be clearly understood fro the following detailed description of a preferred embodiment of the invention, when read in con- 2 junction with the accompanying drawings, in which:

Fig. 1 is a fragmentary, horizontal, sectional view of an extruding lapparatus illustrating certain features of the invention, and

Fig. 2 is an enlarged, fragmentary, vertical, sectional view taken on line 2-2 of Fig. 1.

Referring now in detail to. the drawings, an extrusion cylinder 20 vhas formed therein a cylindrical bore 2l, in which a stock screw 22 rotated by a suitable source of power (not shown) is mounted for thepurpose of forcing an insulating material 24 through an extruding head, designated generally by the numeral 25. The extruding head 25 comprises a body member 26 provided with an opening 2l, which forms a continuation of the bore 2| and which `communicates with a cylindrical bore 28 formed in the head transversely of the opening 21.

Slidably mounted within the bore 28' is a cylindrical tool holder 30 having a central cylindrical bore 3l extending coaxially with the bore 28. A plug 32 and an annular cap 33 secure the tool holder against endwise vmovement in the bore 28, and a key 34 prevents rotation of rthe tool holder in the bore 28. The tool holder 30 lis provided with a tapered opening 40 leading transversely into the bore 3l, and also has a tapered socket 42 formed in one end thereof. .The tool holder may be inserted longitudinally into the bore 28 through a tapped portion 44 of the bore 28y and secured therein by the plug 32. A tubular deector 48 fits in the bore 3| and is secured therein in an oriented position by a `pin 50 fitting into a notch 52 formed radially in the tool holder. The deector is provided with deflecting surfaces 54, 55 and '56, which deilect material forced into the opening 40 tothe left, as viewed in Fig. 1. A wire-guiding tube having a threaded end portion S2 and a frustoconical end socket 64 ts closely but slidably in the tubular deilector. A tubular spacer 12 is provided Vwith a tapped portion '14 designed to be screwed over the threaded end portion 62 of the tube 5U to lock the tube 60 to the spacer 12. The spacer l2 has a threaded portion 'I6 designed to be threaded into a tapped portion I8 of a lock nut 19 to force the tube l6l) tightly against a frustoconical end of a core tube 82, which end ts into the socket 64.

The annular cap 33 having a tapped bore 86 therein is bolted to the body member 26, and holds the cylindrical tool lholder 30 in the bore 28. A generally cylindrical spider 92 having a tapered end 94 complementary to the socket 42 in the tool holder is mounted in a counterbore 88 with a at side face 96 of the spider in contact with a fiat face 98 of an arcuate aligning plate |08 fastened to the tool holder by studs IGZ-|82. The spider is provided with a hub |84 supported coaxially with respect to an outer ring |08 thereof by equally spaced radial arms |88- |08. Each of the arms IUS-|08 is streamlined, and has a rounded forward edge l and a sharp rear edge I2.

The core tube 82 has a tapered nose H5 and a core passage IIS, and fits into the hub |04. A shoulder |28 formed on the core tube is designed to abut an end of the hub.

A generally cylindrical die 24 vI'lts into the tool holder 30, and has a flat sidelface |26 which ts against the aligning plate |00. The die is provided with a passage |28 of which a portion |38 is cylindrical and a portion |32 is tapered. A threaded plug |34 provided with sockets |36- |38 designed to receive a prong wrench (not shown) yis screwed into the tapped bore 86 in the cap 33, and holds a tapered end portion |38 of the die against a complementarily tapered portion |40 of the spider. This holds the frustoconical endl portion 84 of the spider in the socket 42 formed in the tool holder. The spacer 'I2 holds the tube 68 tightly against the frustoconical end 80 of the core tube 82, and holds the shoulder |20 of thecore tube against the end of the hub |84 of the spider, which locates the tapered end ||6 ofthe core tube in a predetermined position longitudinally `with respect to the die |24 and aligned with the die.

'A `Operation An insulating compound including as its essential'constituent an organic, plastic material, such as a thermoplastic or a thermosetting insulating or jacketing material, is forced by the stock screw 22 through the extrusion cylinder 20 into the tapered opening `4,0 in the tool holder Siland into the open portions of the bore 3| in the tool holder 30. The deiiector 48 deiiects the compoundtoward the left, as viewed in Fig. 1, through an angle of 90", and the material ows to the left through the bore 3| around the tube 60, through the spider 92 between the streamlined arms IDS-l 08, through the tapered annular space between the core tube 82 and a portion of the tapered portion 32 of the passage |28 in the die |24. and then through the rest of the tapered portion |32 and the cylindrical portion liiof the passage |28. The die forms thecompound into a covering |50 over the conductor l2 as the cornpound ,flows therethrough.

Asthe compound 24 is forced from the opening 40 into the bore 3| in the tool holder 30, around the wire-guiding tube BD, and-.is deflected to the left, asviewed in Fig 1 .,the pressure of the compound in the area generally below the tubeV 6|) is less than that ofthe compound in the rest of the area around the tube 60. However, as the compound is forced the long distance between the deiiector 48 and the left hand end of the core tube 82, the pressures on the compound in all portions of the cross-sectional area of the passage ofV flow are equalized by the time the compound reaches that end of the core tube, at which end the point of critical clearance between the core tube and the passage |28 in the die |24 is located. Hence, there is no eccentricity in the covering 58. The core tube 82 is held rigidly by the spider 92 and the wire-guiding tube 60, and the die l 24 and the spider are locked inl oriented `positions with respect to each other by the cap 33 and the aligning plate |00 so that their orientation is not aiected by the high extrusion pressures.

The apparatus is simple in construction and operation, and may be assembled and disassembled easily. The tool holder 3U and all the tools held therein may be easily slid out of the head 25 for cleaning or other purposes, another tool holder identical with the tool holder 38 and containing tools like those in the tool holder 30 may be substituted therefor with a minimum interruption of the extrusion operation, and the tools may be removed from the holder 3|) easily and cleaned leisurely.

What is claimed is:

l. An extrusion apparatus, which comprises an extrusion cylinder, an extrusion head connected to one end of the extrusion cylinder and having a passage extending therethrough transversely to the extrusion head, the extrusion head also being provided with an opening aligned axially with respect to the extrusion cylinder and extending through the head to the passage, said opening joining the passage at a point intermediate to the ends of the passage, a tubular tool holder having a passage extending therethrough and also being provided with an opening extending transversely to the passage and intersecting the passage in the tubular holder at a point intermediate the ends thereof, said tool holder being insertable in the passage in the head to a position in which the opening therein is aligned with the extrusion cylinder and the passage therein is aligned with the passage in the head, means for locking the tubular holder in that position, a tubular deector positioned in one end of the passage in the tubular holder, a bushing having a tapped end portion positioned in the last-mentioned end of the pas sage in the extruding head and held therein against longitudinal movement in said passage for holding the plug against movement in the passage, a die mounted in the other end oi' said passage, a core tube positioned in the passage and extending toward the die, the core tube being provided with a shoulder to limit the movement of the core tube toward the die, a spider mounted slidably between the die and the plug for supporting the core tube, means for aligning the spider in the die axially, means for holding the die in the tool holder, and a wire guiding tube provided with a threaded portion for engaging the tapped end portion in the bushing and eX- tending through the bushing and the tubular plug for engaging one end of the core tube and for forcing the shoulder on the core tube against the spider.

2. An extrusion apparatus, which comprises an extruding head having a passage therethrough and a counterbore at one end of the passage, a die held in the open end of the counterbore, a spider positioned in the passage in a position abutting the die and the other end of the counterbore, a core tube having a shoulder thereon supportable by the spider in a position in which the core tube extends toward the die and the shoulder abuts the spider, a tubular dei-lector mounted in the other end of the passage, a guide tube extending through the tubular deiiector to the core tube, and means for locking the guide tube against the core tube to hold the shoulder on the core tube against the spider.

3. An extrusion apparatus, which comprises an extruding head having a passage therethrough, a die held in one end of the passage, a spider positioned in the passage in aposition abutting the die, a core tube having a shoulder thereon sup- REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Number Name Date Webb Jan. 14, 1908 Royle Mar. 24, 1936 Short Mar. 18, 1941 Sonnenfeld Nov. 2, 1948 FOREIGN PATENTS Country Date Great Britain Dec. 1, 1943 

